I have a 50 merc that I love. I can do a ton of ranged aoe dps, decent single target dps and can off heal when needed. not that great of a story, but very fun in pvp. if i need to, i can respec her into a full healer.
i also had a 14 healing operative. the story was great. i deleted him and re rolled him into a sniper cause of the end game shield. i was thinking about end game raids. the problem i had was that i could not stand the game play of both advanced classes. to many situational spells depending if you are in stealth, kneeling down, in cover, etc. got the sniper to 15 and then rerolled him into an assassin.
Now the Assassin is 48. my assassin is fun because i can stealth in and out of combat with decent single target dps. story is interesting and great to play in ovo. my only issue is lack of aoe. there is only one aoe spell and it is not that great. high force cost and low dps. you would think a Double-Bladed lightsaber dps class would have they would include a few cleaves of cone slashes.
I wanted to roll a dps Jug, but i read that the dps jugs do crap damage. I rolled a Marauder and is now 24. dps is great, the story is average and the pvp is fun.
hope that helps.